Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<iostream>
#include<vector>
#include<string>
#include<queue>

int main() {
	int h, w;
	std::cin >> h >> w;
	std::vector<std::string>s(h);
	for (int i = 0; i < h; i++)std::cin >> s[i];
	std::vector<std::vector<int>>score(h, std::vector<int>(w, -1));

	std::queue<std::pair<int, int>>q;
	q.push(std::make_pair(0, 0));
	score[0][0] = 1;
	int dx[4] = { 0,0,1,-1 };
	int dy[4] = { 1,-1,0,0 };

	int white = 0;
	for (int i = 0; i < h*w; i++) {
		if (s[i / w][i%w] == '.')white++;
	}
	
	while (!q.empty()) {
		int x = q.front().first;
		int y = q.front().second;
		q.pop();
		for (int i = 0; i < 4; i++) {
			int nx = x + dx[i];
			int ny = y + dy[i];
			if (nx == -1 || ny == -1 || nx == w || ny == h)continue;
			if (s[ny][nx] == '#')continue;
			if (score[ny][nx] >= 1)continue;
			q.push(std::make_pair(nx, ny));
			score[ny][nx] = score[y][x] + 1;
		}
	}
	printf("%d\n", score[h - 1][w - 1] == -1 ? -1 : white - score[h - 1][w - 1]);
}